>>>>in time will it become illegal to remap any car away from the manufacturers specification<<<<

Isn't it already, if you apply the same criteria for modifying/removing DPFs?

"under the Construction and Use Regulations (more specifically, Regulation 61A of the Road Vehicles (Construction and Use) Regulations) it is illegal to use a vehicle on the road if it has been modified in such a way that it no longer meets the air quality emissions standards that it had to when originally produced."